Typeerror: unhashable type: list

The Python TypeError: unhashable type: 'list' usually means that a list is being used as a hash argument. This error occurs when trying to hash a list, which typeerror: unhashable type: list an unhashable object. For example, using a list as a key in a Python dictionary will cause this error since dictionaries only accept hashable data types as a key. The standard way to solve this issue is to cast a list to a tuple, which is a hashable data type.

Explore your training options in 10 minutes Get Started. Python dictionaries only accept hashable data types as a key in a dictionary. A list is not a hashable data type. In this guide, we talk about what this error means and why you see it in your code. Dictionaries have two parts: keys and values.

Typeerror: unhashable type: list

The TypeError: unhashable type: 'list' usually occurs when you try to use a list object as a set element or dictionary key and Python internally passes the unhashable list into the hash function. But as lists are mutable objects, they do not have a fixed hash value. The easiest way to fix this error is to use a hashable tuple instead of a non-hashable list as a dictionary key or set element. This is not a trivial problem because Python lists are mutable and, therefore, not hashable. In fact, the error can be reproduced most easily when calling hash lst on a list object lst. Because you cannot successfully pass a list into the hash function, you cannot directly use lists as set elements or dictionary keys. The easiest way to fix the TypeError: unhashable type: 'list' is to use a hashable tuple instead of a non-hashable list as a dictionary key. The error may also occur when you try to use a list as a set element. To fix the TypeError: unhashable type: 'list' when trying to use a list as a set element is to use a hashable tuple instead of a non-hashable list. For example, whereas set. If you want to convert a list of lists to a set, you can check out my detailed tutorial on the Finxter blog:. In both cases, we used the string representation of the list instead of the list itself. The string is immutable and hashable and it fixes the error. But what if you really need a mutable set or dictionary key?

The example typeerror: unhashable type: list demonstrates how to add a list into a dictionary as a value. Hashable objects in Python int, float, decimal, complex, bool, string, tuple, range, frozenset, bytes Unhashable objects in Python list, dict, set, bytearray, user-defined classes.

This error occurs when you try to use a list as key in the dictionary or set. As you know 'list' is an unhashable object that can not be used as a key for any dictionary or set. In simple terms, this error occurs when you try to hash a 'list' , which is an unhashable object. To fix this error, you can convert the 'list' into a hashable object like 'tuple' and then use it as a key for a dictionary as shown below. To fix this error, you can convert the 'list' into a hashable object like tuple then use it as a key for 'set' as shown below:. In python, hashing is the method of encoding the data into a fixed-size integer which represent the original value.

For example, using a list as a key in a Python dictionary will throw the TypeError because you can only use hashable data types as a key. This tutorial will go through the error in detail and how to solve it with the help of code examples. TypeError occurs whenever you try to perform an illegal operation for a specific data type object. In the example, the illegal operation is hashing, and the data type is List. By definition, a dictionary key needs to be hashable.

Typeerror: unhashable type: list

This article will discuss the TypeError: unhashable type: 'list' and how to fix it in Python. Dictionaries is a data structure in Python that works in key-value pairs, every key has a value against it, and to access the values of values, you will need the keys like array indices. We have used a list ["a","b"] as the key , but the compiler has thrown a TypeError: unhashable type: 'list'. The hash function is used to find the hash value of a given object, but the object must be immutable like string , tuple , etc. To fix the TypeError in Python, you have to use immutable objects as the keys of dictionaries and as arguments to the hash function. Notice in the above code the hash function works perfectly with mutable objects like tuple and string. This time we provide a string "a" as the key, which is fine to work with because strings are mutable. Zeeshan is a detail oriented software engineer that helps companies and individuals make their lives and easier with software solutions. TypeError: unhashable type: 'list'. Hash of a string object Hash of a tuple object Hash of a string message

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Any student whose average grade on their last three tests is over 75 was added to the dictionary. This characteristic finds significance primarily in the context of dictionary keys. In fact, the error can be reproduced most easily when calling hash lst on a list object lst. For example, using a list as a dictionary key is infeasible since lists aren't hashable. While working as a researcher in distributed systems, Dr. The standard way to solve this issue is to cast a list to a tuple, which is a hashable data type. Explain how python is interpreted How do I install pip on Windows? Once suspended, itsmycode will not be able to comment or publish posts until their suspension is removed. What's Next? What is the purpose pass statement in python? Log in Create account. What is the process of compilation and Loading in python? Is monkey patching considered good programming practice?

Do you know what to do to fix it? For example, as an item of a set or as a key of a dictionary.

The TypeError: unhashable type: 'list' usually occurs when you try to use a list object as a set element or dictionary key and Python internally passes the unhashable list into the hash function. James has written hundreds of programming tuto Managing errors and exceptions in your code is challenging. Each dictionary contains two keys: name and grades. To resolve this, consider using tuples, which are immutable and can serve as hashable alternatives in such contexts. Ayowande Oluwatosin - Feb 2. How do you protect Python source code? How to determine the type of instance and inheritance in Python Python Inheritance How is Inheritance and Overriding methods are related? Feel free to check out more free tutorials and cheat sheets for learning and improving your Python skills in our free email academy:. While working as a researcher in distributed systems, Dr. In python, hashing is the method of encoding the data into a fixed-size integer which represent the original value.